The present invention relates to a sustainedly vapor-releasing body, which is suitable for mass production, to emit the active vapor of a vaporizable substance contained therein over a long period of time or, more particularly, to a sustainedly vapor-releasing body formed of a capillarly tubing containing the vaporizable substance exhibiting an activity in the vapor phase and having excellent shape-retainability to retain its configuration as bent or deformed without heating so that it can very easily and conveniently be installed and kept or settled stably at any desired place where the activity of the released vapor should be exhibited consequently resulting in the full accomplishment of the object of using such a vapor-releasing body over a long period of time and in the full utilization of the activity of the vaporizable substance.
In recent years, there is a great demand to develop an efficient and convenient means to sustainedly and continuously emit vapors of certain vaporizable substances utilized in the vapor form, which include aromatic compounds, pesticides, bactericides, fungicides, sex pheromones of pests and the like distinctly effective even when present in the air in a trace concentration, into the atmosphere in an extremely low concentration.
Suitable for such a purpose of sustainedly vapor-releasing bodies are the so-called microcapsules, for example, disclosed in the specifications of the U.S. Pat. Nos. 3,539,465 and 3,577,515 according to which the vaporizable substance is contained in the microcapsules and emitted through the very thin walls of the microcapsules at a sustained rate. Microcapsules used for such a sustainedly vapor-releasing purpose are, however, disadvantageous in several aspects. For example, the process of microencapsulation costs very high and considerable amounts of the vaporizable substance are lost during the process of microencapsulation so that the products are necessarily very expensive. In addition, due to the fine particulate form of the microcapsules, it is rather a difficult matter to install the sustainedly vapor-releasing body at a desired place where the activity of the vaporizable substance should be exhibited with lastingness over a long period of months or longer notwithstanding the essential necessity in the practice of such lasting installation to fully accomplish the object of sustained vapor releasing. Therefore, microcapsules have not yet acquired very wide prevalence as a form of the sustainedly vapor-releasing body of the above described type.
An alternative form of the sustainedly vapor-releasing body is described in Japanese Patent Kokai No. 52-55969 according to which the vaporizable substance is contained in a hollow fiber with a sealed end and the vapor of the vaporizable substance is emitted gradually through the other open end of the hollow fiber. The process of preparing such a sustainedly vapor-releasing body is simpler with smaller loss of the vaporizable substance in the course of filling the hollow fiber than in the above mentioned method of microencapsulation resulting in less expensiveness of the products so that the sustainedly vapor-releasing bodies of this form are under practical use to some extent.
One of the serious problems in this form of the sustainedly vapor-releasing bodies is again in the stable installation of the bodies at a desired place where the activity of the vaporizable substance should be exhibited over a long period of time. In order to solve this problem, the use of an adhesive is suggested such that the hollow fiber is coated with an adhesive on at least a part of the outer surface thereof and adhesively bonded to the desired place or to the surface of a second body to which the sustainedly vapor-releasing body is to be bonded. Such a method of using an adhesive is very unsatisfactory from the practical standpoint, especially, when the sustainedly vapor-releasing bodies are to be installed on a living plant of the field such as farms and forests by use of an pesticide, fungicide or sex pheromone as the vaporizable substance which is effective only when the vapor thereof is emitted around the living plant since it is almost impossible to obtain lasting adhesive bonding of a foreign body on to the surface of a living plant without imparting any damages or adverse effects to the plant.
As a remedy for the above described difficulty in the use of an adhesive as a means for the installation of a sustainedly vapor-releasing body of the hollow fiber or capillary tubing type, there is also proposed the use of a thread, string or wire which is connected to the fiber or capillary tubing at one end and the other end thereof is fastened by tying or hanging to plants. Although this method is surely effective in obtaining stability of the installation of the sustainedly vapor-releasing body over a long period of time without imparting damages to the body of the plant, there is a fatal problem in this method when applied to a large-scale field work since the work of connecting the thread, string or wire with the fiber or capillary tubing can be undertaken only by handworks and is so much time-consuming that the applicability of this method is limited only to small-scale research works or testing purposes with no promising possibiiity of wide applicability to the large-scale field works.